The interface between a device and a thermal sink is in the technical field of chip packages a dominant thermal resistance. For high-power electronic packages, chip hot-spots and cross-chip temperature gradients represent a significant portion of the total thermal resistance from chip to ambient. Microprocessor chips display non-uniform spatial power distribution with regions of concentrated heat flux. This results in significant temperature gradients within the chip. Since the maximum chip temperature is often the parameter that dictates the thermal reliability of electronic packaging, techniques of reducing chip temperature gradients are becoming important along with traditional techniques of reducing the package internal and external thermal resistance.
For reducing the thermal resistance between hotspots of a chip and a cooling device, it is known to use standoffs between the chip and a cooling device, wherein a paste with a low thermal resistance is displaced between the cooling device and the chip, filling up the volume between the standoffs, the chip and the cooling device. The standoffs improve the thermal conductivity between the chip hotspots and the cooling device; see for example Michael S. June and Kamal K. Sikka, “Using Cap-Integral Standoffs To Reduce Chip Hot-Spot Temperatures In Electronic Packages”, Inter Society Conference on Thermal Phenomena, 2002, IEEE, pages 173 to 178.
Using standoffs between a chip and a cap is also known for enhanced cooling of single flip-chip electronic modules. The chip is between a substrate and a cap, wherein between the cap and the chip a thermal paste and standoffs are arranged; see e.g. K. K. Sikka et al., “Gap-Reduced Thermal Paste Package Design For Cooling Single Flip-Chip Electronic Modules”, 2002 IEEE, Inter Society Conference on Thermal Phenomena, pages 651 to 657.
In U.S. Pat. No. 5,345,107, a cooling apparatus for an electronic device is disclosed that comprises a cooling solid body in close contact through a thermal conductive fluid with a heat transfer portion of the electronic device. On its one surface in contact with the electronic device, a number of grooves communicating with the outside of the heat transfer portion are arranged. A spring member for elastically pressing this cooling solid body on the electronic device is provided for forcing the cooling solid body into close contact with the electronic device by means of the thermal conductive fluid in a third layer. For transferring heat from the chip to a cooling device, a solid thermal conductor is arranged that comprises a number of grooves, each communicating with the outside of the heat transfer surface. The grooves are arranged in a perpendicular structure on the heat transfer surface and the capacity of the grooves is arranged to be larger than the volume of the high thermal conductive grease surrounded by the grooves and applied between two heat transfer surfaces. This construction allows the solid thermal conductor to be brought into close contact with the microchip carrier through the usually stable and thin high thermal conductive grease layer.
U.S. Pat. No. 5,052,481 describes a high conduction cooling module having internal fins and compliant interfaces for VLSI chip technology. A finned internal thermal device having a flat bottom contacts the chips, while corresponding trenches in a cooling hat mounted to a cold plate form gaps into which the fins of the finned internal thermal devices are slidably mounted. On a backside of the finned thermal device, grooves are arranged in a perpendicular structure. The grooves may be between 15 and 20 μm wide and deep, and spaced approximately 0.25 mm apart.